Today, computing devices such as personal computers, laptop computers, personal digital assistants, cell-phones, etc., are routinely used at work, home, and everywhere in-between. Computing devices advantageously enable the use of application specific software, file sharing, the creation of electronic documents, and electronic communication and commerce through the Internet and other computer networks. Typically, each computing device has a storage peripheral such as a disk drive.
A huge market exists for disk drives for mass-market computing devices such as desktop computers, laptop computers, as well as small form factor (SFF) disk drives for use in mobile computing devices (e.g., personal digital assistants (PDAs), cell-phones, digital cameras, etc.). To be competitive, a disk drive should be relatively inexpensive and provide substantial capacity, rapid access to data, and reliable performance.
Disk drives typically comprise a disk and a head connected to a distal end of an actuator arm which is rotated by a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk typically comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo sectors. The servo sectors typically comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the velocity of the actuator arm as it seeks from track to track.
Data is typically written to the disk by modulating a write current in an inductive coil to record magnetic transitions onto the disk surface. During readback, the magnetic transitions are sensed by a read element (e.g., a magnetoresistive element) and the resulting read signal demodulated by a suitable read channel.
To be competitive in the hard disk drive market, a hard disk drive should be relatively inexpensive and should embody a design that is adaptive for low-cost mass production, while at the same time provide high data storage capacity and provide rapid access to data. Satisfying these competing restraints of low-cost, high data storage capacity, rapid access to data and improved reliability requires innovation in each of the numerous components of the disk drive, methods of assembly, and in testing. One way to satisfy these competing restraints is by purchasing and utilizing disks (i.e. media) at particular price points, which have some amount of expected disk defects, and margining these disk defects during verification testing of the disk drive before ultimately sending the disk drive out to a customer.
Currently, during disk drive functionality testing, before burn-in and before the disk drive is sent out to the customer, the disk is scanned for defects that are the result of, for example, scratches and/or thermal asperities on the disk. The entire surface of the disk may be scanned and a map or a table of detected defect patterns may be generated. Based upon the amount of detected defects it may be determined whether the disk drive is useable or not. The disk drive may fail the manufacturing process when to many defects are detected. In present methods, if the disk drive does not fail, as to the defects that are detected, only a minimal area corresponding to each detected defect is removed from data storage and this defect may spread during subsequent disk drive usage and the disk drive may ultimately fail for the disk drive purchaser. In particular, no additional margin around the detected defect areas is accounted for to provide better disk drive reliability.
Therefore, there is a need in the disk drive manufacturing process to enable further defect margining around detected media defects.